1. Field of the Invention
The present invention relates to a development sensor apparatus and, more particularly, to a development sensor apparatus for obtaining the progression of development of an optical disk master.
2. Description of the Related Art
According to a conventional development sensor apparatus, as shown in, e.g., Japanese Patent Laid-Open Nos. 59-171957, 60-212832, and 1-298356, and "National Technical Report", Vol. 29, No. 5, p. 106, Oct. 1983, 0th- and 1st-order diffracted light components obtained by radiating a laser beam on the pattern surface of a photoresist substrate under development are directly received by optical detection units, the positions of which relative to a radiation point on the pattern surface are fixed, and the ratio of these diffracted light components is calculated from detection signals of the respective diffracted light components.
FIG. 3 shows the main part of a conventional development sensor apparatus.
Referring to FIG. 3, a monitoring laser beam L incident on the lower surface of a master 51 during development is diffracted by a photoresist pattern formed on the master 51 in accordance with the progress of development. 0th- and 1st-order diffracted light components L0 and L1 are respectively received by optical sensors 52 and 53.
A diffracted light ratio calculating unit 60 calculates the ratio of the diffracted light from a detection signal a output from the optical sensor 52 upon reception of the 0th-order diffracted light component L0 and a sensor signal b output from the optical sensor 53 upon reception of the 1st-order diffracted light component L1, and outputs a development monitor signal c. Thus, the progression of development of the optical disk master can be detected outside the developing unit. In this case, the developing unit stops development when the diffracted light ratio reaches a desired value.
The direction of the optical axis of the 1st-order diffracted light component is changed by the flowed state of the developing agent flowing on the photoresist substrate or the eccentricity of the photoresist substrate from a substrate rotating unit obtained when the photoresist substrate is installed on the substrate rotating unit. However, in the conventional case, since the 1st-order diffracted light component is directly received by the optical sensor 53, the position of which relative to the radiation point of the monitoring laser beam on the photoresist substrate is fixed, the light-receiving position on the light-receiving surface of the optical sensor 53 undesirably changes. Thus, due to variations in light-receiving sensitivity of the optical sensor 53 within the light-receiving surface, the progression of development cannot be accurately monitored.
In this case, when the light-receiving sensitivity of the optical sensor 53 varies by about several %, it causes variations in level of the development monitor signal c, thereby causing variations in the shape of the formed pattern.
Furthermore, when patterns formed on the photoresist substrate have different pitches, the 1st-order diffracted light components have different diffraction angles. Thus, a cumbersome and skilled operation is required for position adjustment and the like of the optical sensor 53 that receives the 1st-order diffracted light components.